Now, for a fairly large number of devices of this type which easily allow the arc to be quenched without switching in a resistor, it is generally preferable for the closing resistance to be switched in only before the main contacts close and to avoid switching in the resistance during arc interruption.
The above disposition avoids the need to install an arc interrupter unit on the resistance switch-in contacts and makes it possible to reduce the dimensions of the resistance. The dispositions of the prior art consist in connecting an auxiliary closing chamber in parallel with the main chamber of the circuit-breaker, e.g. as described in French patent application No. 77 25 777. However, such dispositions are always bulky and therefore expensive.
The invention aims to provide a less bulky resistance switch-in device which operates when a circuit breaker closes with a more economical cost price.